The Ford Barn

Steve in Denver · 10-20-2023, 07:56 AM

I have an 8BA in my '36 with a 12 volt system. The Tach is not working and it did before. Not sure what I changed. The Positive side of the coil is going to the distributor and the Tach wire is hooked to the same positive lug.

Should I have the negative side of the coil going to the distributor and the Tach wire hooked to it?

GB SISSON · 10-20-2023, 08:51 AM

If your vehicle is wired as negative ground, the negative side of coil runs to the distributor. If positive ground, then that terminal to the distributor. Check your battery for which side is run to ground as a guide. Like many others, when I switch to 12v, I switch to negative ground. When built your car was 6v with positive ground.

40cpe · 10-20-2023, 08:56 AM

Assuming you have a 12V NEGATIVE grounded battery installation, the negative side of the coil should go to the distributor. The sensor wire from the tach should also be on the side going to the distributor.

GB was posting while I was typing

Steve in Denver · 10-20-2023, 11:32 AM

Just Checked. Definitely Negative ground on the 12 volt system, so I have my coil in backwards.
Great way to remember, Negative Ground, Negative from the coil to the distributor.
Thanks

JayChicago · 10-20-2023, 12:27 PM

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Yep.
And the tach is always connected to the distributor side of the coil. The tach measures RPM by counting the pulses created by opening/closing of the points in the distributor.

10-20-2023, 07:56 AM	#1
Steve in Denver Senior Member Join Date: May 2017 Posts: 566	8BA, 12v coil question I have an 8BA in my '36 with a 12 volt system. The Tach is not working and it did before. Not sure what I changed. The Positive side of the coil is going to the distributor and the Tach wire is hooked to the same positive lug. Should I have the negative side of the coil going to the distributor and the Tach wire hooked to it? __________________ Steve in Denver

10-20-2023, 08:51 AM	#2
GB SISSON Senior Member Join Date: Jan 2014 Location: Orcas Island Washington Posts: 4,941	Re: 8BA, 12v coil question If your vehicle is wired as negative ground, the negative side of coil runs to the distributor. If positive ground, then that terminal to the distributor. Check your battery for which side is run to ground as a guide. Like many others, when I switch to 12v, I switch to negative ground. When built your car was 6v with positive ground. __________________ Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)

10-20-2023, 08:56 AM	#3
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,024	Re: 8BA, 12v coil question Assuming you have a 12V NEGATIVE grounded battery installation, the negative side of the coil should go to the distributor. The sensor wire from the tach should also be on the side going to the distributor. GB was posting while I was typing

10-20-2023, 11:32 AM	#4
Steve in Denver Senior Member Join Date: May 2017 Posts: 566	Re: 8BA, 12v coil question Just Checked. Definitely Negative ground on the 12 volt system, so I have my coil in backwards. Great way to remember, Negative Ground, Negative from the coil to the distributor. Thanks __________________ Steve in Denver

10-20-2023, 12:27 PM	#5
JayChicago Senior Member Join Date: Jan 2019 Location: Chicago Posts: 732	Re: 8BA, 12v coil question Sponsored Links (Register now to hide all advertisements) Yep. And the tach is always connected to the distributor side of the coil. The tach measures RPM by counting the pulses created by opening/closing of the points in the distributor.